The acronym xDSL refers collectively to a number of variations of the DSL (Digital Subscriber Line) technology, which aims at utilizing the information transmission capability of ordinary copper wires to the ultimate possible extent. Known variations that go under the umbrella definition of xDSL are at the priority date of this patent application ADSL (Asymmetric Digital Subscriber Line), CDSL (Consumer DSL, registered trademark of Rockwell International Corp.), G.Lite (also known as DSL Lite, splitterless ADSL, and Universal ADSL; officially ITU-T standard G-992.2), HDSL (High bit-rate DSL), RADSL (Rate-Adaptive DSL), SDSL (Symmetric DSL), VDSL (Very high data rate DSL) and even to some extent UDSL (Unidirectional DSL), which is only a proposal, and IDSL (ISDN DSL), which is actually closer to ISDN (Integrated Services Digital Network).
FIG. 1 illustrates the known hierarchical structure of an xDSL network. In this description we will refer to the levels of the structure as level 1, level 2, level 3 and level 4. Level 1 comprises the user-end devices, of which devices 101, 102, 103, 104, 105 and 106 are shown in FIG. 1. The number of devices on level 1 can be very large in a fully deployed xDSL network, since there is at least one user-end device per each subscriber. The task of a user-end device is to act as a gateway between an xDSL line 107 and the user's own local network; the term “local network” should be understood widely so that it covers also a single computer device at the user's. On level 2 there are the lowest-level xDSL switches that are in direct connection with end-user devices and concentrate the connections to and from them into a backbone network. xDSL switches 111, 112 and 113 are shown. The number of lowest-level xDSL switches is still relatively high: there may be for example one lowest-level switch per 30 user-end devices.
Level 3 comprises higher-level xDSL switches 121 that act as multiplexers/demultiplexers between connections 114 to several lowest-level xDSL switches and a high-capacity trunk network 122 such as an ATM (Asynchronous Transfer Mode) network. The xDSL switches are also known as DSLAMs (DSL Access Multiplexers). The number of hierarchical levels that consist of xDSL switches is in general not limited but depends on such factors as the geographical coverage of the network, number of subscribers and overall architecture of the network.
Level 4 comprises one or more network managing stations 131 the task of which is to maintain databases 132 of configuration information for all network elements in the xDSL network. A network managing station 131 also offers the means for the operator of the network to manage and control the operation of the whole xDSL network. In a small xDSL network one of the xDSL switches (DSLAMs) can also act as a network managing station.
In addition to the so-called active network elements shown in FIG. 1 the xDSL network may contain other devices such as repeaters and amplifiers. However, these are known in the xDSL technology as “passive” devices and are not important to the scope of the present invention.
Configuration information is a general term that means all such information that an active network element in an xDSL network needs for properly fulfilling its functional tasks in the network. The scope of the concept “configuration information” is not meant to be limited further in the present patent application, because the invention is equally applicable both to configuration information known at the priority date of the application and to future extensions of the concept. As an example, a user-end device needs to know, how the local network of the user is coupled to the outside world and what kind of limitiations are applicable to communications through the xDSL connection. Lowest-level xDSL switches need to know, which subscribers are connected and what is the level of service and data transmission rate that should be provided to each subscriber. Similarly higher-level xDSL switches need to know, with which lower-level elements they are communicating with and what are the characteristics of each of these connections.
In a prior art xDSL network such as the one shown in FIG. 1 it has been customary to store all configuration information centrally in the database 132. Changes in configuration information have required the intervention of a trained person who sits at the network management station 131 and types in the commands for changing the configuration. Each time when a network element needs to be configured anew, or when a network element needs to revert to a piece of configuration information that existed previously but has become somehow temporarily unavailable, the network element must establish a communication connection to the network management station. In a worst case the configuration of a network element can not be changed or restored before a human operator has paid attention to the situation at the network management station and taken appropriate measures. A single fault at level 4 can disable a whole xDSL network because configuration information can not be obtained.